Write Pole Laser Power Monitoring via Resistance
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Solution Overview
Problem
Thermally assisted magnetic recording disk drives face challenges in monitoring laser light power without adding additional components or costs, due to the small size constraints and complexity of integrating photodiodes, which are necessary for accurate power measurement.
Innovation Solution
The system utilizes existing elements on the magnetic head, such as a write pole or heat absorbing sensors, to measure temperature-dependent electrical resistance changes caused by laser light, allowing for the determination of laser power levels without additional components, using a measurement module and interface module to report the power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photodiode is added to monitor laser power, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent makes the write pole serve dual functions: its primary function of writing magnetic data and a secondary function of sensing laser power through temperature-dependent resistance changes. This eliminates the need for a separate photodiode component while enabling laser power monitoring capability.
Solution Approach 2:
The write pole uses its own inherent property (temperature-dependent electrical resistance) to monitor laser power. The component monitors itself by detecting temperature changes caused by absorbed laser energy, eliminating the need for external monitoring components.
2Measurement precision
If a photodiode is added to monitor laser power, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The write pole is designed to perform multiple functions including data writing and laser power sensing, eliminating the need to manufacture and integrate additional photodiode components, thereby reducing manufacturing complexity and cost.
Solution Approach 2:
The patent combines the laser sensing function with the existing write pole structure by utilizing its temperature-dependent resistance property. This merging of functions eliminates separate components and reduces overall manufacturing cost.
3Measurement precision
If a photodiode is added to monitor laser power, then measurement precision is improved, but the number of electrical leads increases
Solution Approach 1:
The write pole uses existing electrical leads for its primary function to also carry measurement signals for laser power monitoring. This eliminates the need for separate dedicated leads for photodiode connections, reducing lead count and complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate monitoring of laser power within thermally assisted magnetic recording systems, ensuring reliable data storage by maintaining magnetic stability at room temperature while avoiding the need for additional components, thus reducing costs and complexity.
Implementation Method 1
A portion of the laser light is absorbed by the write pole, heating the write pole
Implementation Method 2
the temperature dependent electrical resistance of the head elements can be measured
Data Source
AI summary
An apparatus, system, and method for measuring thermally induced electric resistance changes in thermally assisted magnetic recording are disclosed for monitoring laser light output in thermally assisted magnetic recording disk drives. An electrical lead is coupled to a read/write head element. A first electrical resistance in the read/write head element is measured. The read/write head is heated by a laser and a second electrical resistance in the read/write head element is measured. The electrical resistance may be monitored at regular intervals when the read/write head element is on the ramp or the electrical resistance measurements may be continuously monitored as the read/write head flies over the magnetic media.